The purpose of the Real-time Quantitative PCR Core is to assist investigators in evaluating gene transfer efficiency and transgene expression in target cells for projects in the Gene Therapy for Metabolic Disorders program. As initially demonstrated by a gene therapy clinical trial ("Lymphocyte gene therapy for Hunter syndrome), this technique fills a very significant scientific need, to accurately quantitate the presence of a gene, and to measure its expression by reverse transcriptase-PCR (RT-PCR) with a high level of sensitivity and reproducability. This core will assist investigators in designing assay systems (paired oligonucleotide primers and an internal TaqMan probe, Black Hole Quencher probe, or SYBR Green), as well as accomplish the actual assays of research specimens. The availability of a core facility accomplishing assays for common biologic systems (e.g., gene and gene products for OTC, MPS I, and MPS VII mouse models) eliminates redundancy and provides a greater level of quality assurance. The new, quantitative technology also provides sensitive methods for "safety assays" (e.g., for lentiviral vector RCR) that are much faster, reliable and inexpensive in comparison to existing culture approaches. The technique also provides a method of quantitating gene products (RT-PCR) for which there are no existing assays, or for DNA sequences that do not yield a translational or transcriptional end product (as might be needed for transposon vectors).